1TPMLIB_REGISTERCALLBACKS(1) libtpms documentation TPMLIB_REGISTERCALLBACKS(1)
2
6 TPMLIB_RegisterCallbacks - Register callbacks for implementing
7 customized behavior of certain functions
8
10 TPM library (libtpms, -ltpms)
11
13 #include <libtpms/tpm_types.h>
14 #include <libtpms/tpm_library.h>
16 #include <libtpms/tpm_error.h>
18 TPM_RESULT TPMLIB_RegisterCallbacks(struct tpmlibrary_callbacks *);
20
22 The TPMLIB_RegisterCallbacks() functions allows to register several
23 callback functions with libtpms that enable a user to implement
24 customized behavior of several library-internal functions. This feature
25 will typically be used if the behavior of the provided internal
26 functions is not as needed. An example would be that libtpms writes
27 all data into files with certain names. If, however, the data needs to
28 be written into a special type of storage the user will register
29 callbacks with the library that are invoked when the TPM needs to
30 write, read or delete data from storage and the user may then implement
31 custom behavior in these functions.
32 The following shows the data structure used for registering the
34 callbacks.
35 struct libtpms_callbacks {
37 int sizeOfStruct;
38 TPM_RESULT (*tpm_nvram_init)(void);
39 TPM_RESULT (*tpm_nvram_loaddata)(unsigned char **data,
40 uint32_t *length,
41 uint32_t tpm_number,
42 const char *name);
43 TPM_RESULT (*tpm_nvram_storedata)(const unsigned char *data,
44 uint32_t length,
45 uint32_t tpm_number,
46 const char *name);
47 TPM_RESULT (*tpm_nvram_deletename)(uint32_t tpm_number,
48 const char *name,
49 TPM_BOOL mustExist);
50 TPM_RESULT (*tpm_io_init)(void);
51 TPM_RESULT (*tpm_io_getlocality)(TPM_MODIFIER_INDICATOR *localityModifer,
52 uint32_t tpm_number);
53 TPM_RESULT (*tpm_io_getphysicalpresence)(TPM_BOOL *physicalPresence,
54 uint32_t tpm_number);
55 };
56 Currently 7 callbacks are supported. If a callback pointer in the above
58 structure is set to NULL the default library-internal implementation of
59 that function will be used.
60 If one of the callbacks in either the tpm_nvram or tpm_io group is set,
62 then all of the callbacks in the respective group should be
63 implemented.
64 tpm_nvram_init
66 This function is called before any access to persitent storage is
67 done. It allows the user to perform initialization of access to
68 persitent storage.
69 Upon success this function should return TPM_SUCCESS, a failure
71 code otherwise.
72 The default implementation requires that the environment variable
74 TPM_PATH is set and points to a directory where the TPM's state can
75 be written to. If the variable is not set, it will return TPM_FAIL
76 and the initialization of the TPM in TPMLIB_MainInit() will fail.
77 tpm_nvram_loaddata
79 This function is called when the TPM wants to load state from
80 persistent storage. The implementing function must allocate a
81 buffer (data) and return it to the TPM along with the length of the
82 buffer (length). The tpm_number is always 0 and can be ignored.
83 The name parameter is either one of TPM_SAVESTATE_NAME,
84 TPM_VOLATILESTATE_NAME, or TPM_PERMANENT_ALL_NAME and indicates
85 which one of the 3 types of state is supposed to be loaded.
86 Upon success this function should return TPM_SUCCESS, a failure
88 code otherwise.
89 The default implementation writes the TPM's state into files in a
91 directory where the TPM_PATH environment variable pointed to when
92 TPMLIB_MainInit() was executed. Failure to write the TPM's state
93 into files will put the TPM into failure mode.
94 tpm_nvram_storedata
96 This function is called when the TPM wants to store state to
97 persistent storage. The data and length parameters provide the data
98 to be stored and the number of bytes. The implementing function
99 must not free the data buffer. The tpm_number is always 0 and can
100 be ignored. The name parameter is either one of
101 TPM_SAVESTATE_NAME, TPM_VOLATILESTATE_NAME, or
102 TPM_PERMANENT_ALL_NAME and indicates which one of the 3 types of
103 state is supposed to be stored.
104 Upon success this function should return TPM_SUCCESS, a failure
106 code otherwise.
107 The default implementation reads the TPM's state from files in a
109 directory where the TPM_PATH environment variable pointed to when
110 TPMLIB_MainInit() was executed. Failure to read the TPM's state
111 from files may put the TPM into failure mode.
112 tpm_nvram_deletename
114 This function is called when the TPM wants to delete state on
115 persistent storage. The tpm_number is always 0 and can be ignored.
116 The name parameter is either one of TPM_SAVESTATE_NAME,
117 TPM_VOLATILESTATE_NAME, or TPM_PERMANENT_ALL_NAME and indicates
118 which one of the 3 types of state is supposed to be deleted. The
119 mustExist parameter indicates wheteher the given data must exist
120 and the implementing function should return TPM_FAIL if the data
121 did not exist.
122 Upon success this function should return TPM_SUCCESS, a failure
124 code otherwise.
125 The default implementation deletes the TPM's state files in a
127 directory where the TPM_PATH environment variable pointed to when
128 TPMLIB_MainInit() was executed. Failure to delete the TPM's state
129 files may put the TPM into failure mode.
130 tpm_io_init
132 This function is called to initialize the IO subsystem of the TPM.
133 Upon success this function should return TPM_SUCCESS, a failure
135 code otherwise.
136 The default implementation simply returns TPM_SUCCESS.
138 tpm_io_getlocality
140 This function is called when the TPM needs to determine the
141 locality under which a command is supposed to be executed. The
142 implementing function should return the number of the locality by
143 writing it into the localityModifier pointer.
144 Upon success this function should return TPM_SUCCESS, a failure
146 code otherwise.
147 The default implementation returns 0 as the locality.
149 tpm_io_getphysicalpresence
151 This function is called when the TPM needs to determine whether
152 physical presence has been asserted. The implementing function
153 should write either TRUE or FALSE into the physicalPresence
154 pointer.
155 Upon success this function should return TPM_SUCCESS, a failure
157 code otherwise.
158 The default implementation returns FALSE for physical presence.
160
162 Upon successful completion, TPMLIB_MainInit() returns TPM_SUCCESS, an
163 error value otherwise.
164
166 TPM_SUCCESS
167 The function completed sucessfully.
168 TPM_FAIL
170 General failure.
171 For a complete list of TPM error codes please consult the include file
173 libtpms/tpm_error.h
174
176 #include <libtpms/tpm_types.h>
177 #include <libtpms/tpm_library.h>
178 #include <libtpms/tpm_error.h>
179 static TPM_MODIFIER_INDICATOR locality;
181 static TPM_RESULT mytpm_io_init(void)
183 {
184 return TPM_SUCCESS;
185 }
186 static TPM_RESULT tpm_io_getlocality(TPM_MODIFIER_INDICATOR *locModif)
188 {
189 *locModif = locality;
190 return TPM_SUCCESS:
192 }
193 static TPM_RESULT mytpm_io_getphysicalpresence(TPM_BOOL *phyPres)
195 {
196 *physicalPresence = FALSE;
197 return TPM_SUCCESS;
199 }
200 int main(void) {
202 TPM_RESULT res;
203 unsigned char *respbuffer;
204 uint32_t resp_size;
205 uint32_t respbufsize;
206 unsigned char *command;
207 uint32_t command_size;
208 struct libtpms_callbacks cbs = {
210 .sizeOfStruct = sizeof(struct libtpms_callbacks),
211 .tpm_nvram_init = NULL,
212 .tpm_nvram_loaddata = NULL,
213 .tpm_nvram_storedata = NULL,
214 .tpm_nvram_deletename = NULL,
215 .tpm_io_init = mytpm_io_init,
216 .tpm_io_getlocality = mytpm_io_getlocality,
217 .tpm_io_getphysicalpresence = mytpm_io_getphysicalpresence,
218 };
219 [...]
222 if (TPMLIB_RegisterCallbacks(cbs) != TPM_SUCCESS) {
224 fprintf(stderr, "Could not register the callbacks.\n");
225 return 1;
226 }
227 if (TPMLIB_MainInit()) != TPM_SUCCESS) {
229 fprintf(stderr, "Could not start the TPM.\n");
230 return 1;
231 }
232 [...]
234 /* build TPM command */
235 [...]
236 res = TPMLIB_Process(&respbuffer, &resp_size,
238 &respbufsize,
239 command, command_size);
240 [...]
241 TPMLIB_Terminate();
243 return 0;
245 }
246
248 TPMLIB_Process(3), TPMLIB_MainInit(3), TPMLIB_Terminate(3),
249 TPMLIB_DecodeBlobs(3)
250libtpms-0.5.1 2011-10-12 TPMLIB_REGISTERCALLBACKS(1)